Ratio shift control system and method for a multiple-ratio automatic transmission

Abstract

A control system and method for controlling a multiple gear ratio automatic transmission in a powertrain for an automatic transmission having pressure activated friction torque elements to effect gear ratio upshifts. The friction torque elements are synchronously engaged and released during a torque phase of an upshift event as torque from a powertrain source is increased while allowing the off-going friction elements to slip, followed by an inertia phase during which torque from a powertrain source is modulated. A perceptible transmission output torque reduction during an upshift is avoided.

What is claimed is: 
     
       1. A multiple-ratio transmission wherein a powertrain source provides an input torque to the transmission comprising:
 oncoming and off-going friction elements for effecting ratio shifts; and 
 a controller, during a ratio upshift event, configured to: 
 increase the input torque from the powertrain source based on a feedback variable of the off-going friction element during a torque phase as the off-going friction element slips, 
 thereby minimizing torque transients to a transmission output during the upshift event. 
 
     
     
       2. The multiple-ratio transmission set forth in  claim 1  wherein the controller is configured to:
 decrease the input torque during a transition from the torque phase to an inertia phase; and 
 increase the input torque at the end of the inertia phase. 
 
     
     
       3. The multiple-ratio transmission set forth in  claim 1 , further comprising a clutch actuator wherein the feedback variable of the off-going friction element is determined by the position of an actuator for the off-going friction element. 
     
     
       4. A control system for a multiple-ratio vehicle transmission comprising:
 a controller for controlling torque capacity of oncoming and off-going friction elements, 
 wherein, during an upshift event, torque control of a powertrain source and the off-going friction element is decoupled from the oncoming friction element, 
 wherein torque control of the powertrain source being independently managed to obtain a controlled increase in torque of the powertrain source during an torque phase and prior to an inertia phase, 
 wherein the controller is adapted to determine a desired level of driving torque and torque of the powertrain source and to self-calibrate a required level of oncoming friction element torque capacity. 
 
     
     
       5. The control system set forth in  claim 4 , wherein the off-going friction element torque capacity is controlled using closed loop control with off-going friction element pressure as a feedback variable. 
     
     
       6. The control system set forth in  claim 5  wherein the off-going friction element torque capacity is open loop controlled. 
     
     
       7. The control system set forth in  claim 5  wherein the control system includes a clutch actuator wherein a feedback variable of the off-going friction element is determined by the position of an actuator for the off-going friction element. 
     
     
       8. The control system set forth in  claim 4 , wherein the controller is configured to control the powertrain source and activating pressure of the off-going friction element to achieve a desired slip of the off-going friction element during the torque phase. 
     
     
       9. The control system set forth in  claim 4 , wherein the controller is adapted to calculate torque transmitted through the off-going friction element to determine an end of the torque phase prior to the inertia phase. 
     
     
       10. The control system set forth in  claim 4 , wherein the controller is adapted to determine an end of the torque phase at an elapsed time from the beginning of the torque phase, a corresponding change in torque of the powertrain source and a corresponding change in input torque. 
     
     
       11. The control system set forth in  claim 4 , wherein the controller is configured to reduce torque of the powertrain source during the inertia phase and increase torque of the powertrain source when the inertia phase ends, whereby input torque change during the inertia phase is reduced. 
     
     
       12. A control system as set forth in  claim 4  wherein the controller is configured to increase torque capacity of the oncoming friction element during the torque phase to effect engagement of the oncoming friction element during the torque phase; and
 the controller is configured to increase torque of the powertrain source during the torque phase as torque capacity of the off-going friction element is reduced during the torque phase to allow slip, 
 whereby the controller manages torque distributed from the powertrain source. 
 
     
     
       13. The control system set forth in  claim 12  wherein the controller is configured to self-calibrate clutch capacity of the oncoming friction element during the torque phase to achieve a desired input torque output profile with respect to time before the upshift event is completed as the off-going friction element slips during the torque phase. 
     
     
       14. The control system set forth in  claim 13  wherein the controller adjusts torque of the powertrain source to maintain slip of the off-going friction element during the torque phase at a desired level. 
     
     
       15. The control system set forth in  claim 14  wherein torque of the powertrain source is adjusted during the torque phase with closed loop control using a measured slip of the off-going friction element as a feedback variable. 
     
     
       16. The control system set forth in  claim 13  wherein the controller is configured to reduce torque of the powertrain source during the inertia phase. 
     
     
       17. The control system set forth in  claim 12  wherein the controller is further configured to establish a preparatory phase prior to the torque phase and to reduce torque capacity of the off-going friction element during the preparatory phase to prepare for its release. 
     
     
       18. A method for controlling an upshift of a multiple-ratio vehicle transmission comprising:
 increasing an input torque from a powertrain source based on a feedback variable of one of an on-coming friction element and an off-going friction element during a torque phase; 
 decreasing the input torque during a transition from the torque phase to an inertia phase until the upshift is substantially ended; 
 decreasing the off-going friction element torque capacity during the torque phase while allowing slip; and 
 increasing an oncoming friction element torque capacity during the torque phase. 
 
     
     
       19. The method set forth in  claim 18  further comprising:
 choosing a desired output shaft torque during the torque phase; 
 choosing a desired off-going friction element torque; 
 calculating an oncoming friction element torque as a function of the desired off-going friction element torque and the desired output shaft torque; 
 controlling an oncoming friction element to achieve the calculated oncoming friction element torque; 
 controlling the powertrain source to achieve a desired off-going friction element slip; 
 adjusting an off-going friction element pressure to achieve the desired off-going friction element torque; and 
 releasing the off-going friction element at the end of the torque phase. 
 
     
     
       20. The method set forth in  claim 19  further comprising determining whether the desired off-going friction element torque is less than a predetermined threshold value before allowing the off-going friction element to be released when the torque phase ends. 
     
     
       21. The method set forth in  claim 20  further comprising determining the oncoming friction element torque during the inertia phase as a function of desired output shaft torque and gear ratio for the oncoming friction element and for the off-going friction element. 
     
     
       22. The method set forth in  claim 18  further comprising: choosing a desired transmission output torque;
 choosing desired off-going friction element slip torque during a torque phase of an upshift; 
 calculating a target input torque as a function of desired transmission output torque and a delta input torque based on the target input torque; 
 choosing a desired off-going friction element torque; 
 calculating a delta off-going friction element torque; 
 calculating oncoming friction element target torque based on delta off-going friction element torque; 
 ramping oncoming friction element torque to the oncoming friction element target torque; and 
 ramping the input torque toward the target input torque, whereby a smooth transition is made to an inertia phase as during which torque of the powertrain source is decreased during the inertia phase. 
 
     
     
       23. The method set forth in  claim 18  further comprising:
 choosing a desired target oncoming friction element torque during a torque phase of an upshift; 
 choosing a desired input torque slip; 
 calculating an input torque of the powertrain source to compensate for the desired target oncoming friction element torque; 
 choosing a desired off-going friction element torque; 
 ramping the oncoming friction element toque toward the target oncoming friction element torque; and 
 ramping the input torque toward the target torque prior to release of the off-going friction element as a transition is made to an inertia phase whereby torque disturbances in torque delivery through the transmission are reduced during an upshift. 
 
     
     
       24. The method set forth in  claim 18  further comprising:
 choosing a desired output shaft torque and a desired slip of the off-going friction element; 
 calculating a target input torque from the powertrain source as a function of desired output shaft torque; 
 calculating an oncoming friction element torque target, based on a desired off-going friction element torque; and 
 increasing torque of the powertrain source toward the target input torque followed by release of the off-going friction element as a transition is made from the torque phase to an inertia phase in the upshift. 
 
     
     
       25. The method set forth in  claim 18  further comprising:
 choosing a desired oncoming friction element torque target; 
 choosing a desired input slip torque; 
 calculating an input torque target for the powertrain source using the oncoming friction element torque target and the desired input slip torque; 
 choosing a desired off-going friction element torque; 
 ramping oncoming friction element torque toward the oncoming friction element target; and 
 ramping input torque from the powertrain source toward the target input torque and releasing the off-going friction element as the torque of the powertrain source is decreased at the start of an inertia phase of the upshift.